Semiconductor devices for use in networks or digital household electric appliances are being further desired to be sophisticated, multifunctional, and low in power consumption. Accordingly, the trend toward micro-patterning for circuits has been developed. With this trend, a pattern collapse in a circuit pattern has been getting serious. In the producing of the semiconductor devices, a cleaning step has been heavily used for the purpose of removing contaminants such as particles and metal impurities, so as to occupy up to 30-40% of the whole of the semiconductor fabrication process. If the aspect ratio of the pattern is increased with the trend toward micro-patterning of the semiconductor devices, the pattern is to collapse when a gas-liquid interface passes through the pattern after cleaning or rinsing. This phenomenon is a pattern collapse.
The pattern collapse occurs at the time of drawing the wafer out of a cleaning liquid or a rinsing liquid. The reason thereof is said that a difference in height of residual liquid between a part having a high aspect ratio and that having a low aspect ratio makes a difference in capillary force which acts on the pattern.
Accordingly, the pattern collapse is excepted to be solved by reducing the capillary force to decrease the difference in capillary force due to the difference in height of the residual liquid. The magnitude of the capillary force is the absolute value of P obtained by the equation as shown below. It is expected from this equation that the capillary force can be reduced by decreasing γ or cos θ.P=2×γ×cos θ/S 
(γ: Surface tension, θ: Contact angle, S: Pattern width).
As a method of decreasing γ to suppress the pattern collapse, there is disclosed in Patent Publication 1 a technique of changing the cleaning liquid from water to 2-propanol before the gas-liquid interface passes through the pattern.
Additionally, as a method for decreasing cos θ to suppress the pattern collapse, there is disclosed in Patent Publication 2 a technique directed toward a resist pattern. This is a method of setting a contact angle to around 90° to bring cos θ near to 0 so as to reduce the capillary force as far as possible, thereby suppressing the pattern collapse.
However, the thus disclosed technique is directed toward the resist pattern and is for reforming a resist itself. Moreover, the resist pattern can be finally removed together with the resist, so that it is not necessary to estimate a method of removing a treatment agent after drying; therefore this technique cannot be applied to the present object.
Additionally, in Patent Publication 3, there is disclosed a cleaning method including: surface-reforming a wafer surface in which an uneven pattern is formed with a silicon-containing film, by oxidation and the like; forming a water-repellent protecting film on the surface by using a water-soluble surfactant or a silane coupling agent; reducing the capillary force; and thereby preventing the pattern collapse.
Furthermore, there is disclosed in Patent Publications 4 and 5 a technique of conducting a water repellency-providing treatment in the use of a treatment liquid including a sililation reagent represented by N,N-dimethylaminotrimethylsilane and a solvent thereby preventing the pattern collapse.